From: Eric Biggers <ebiggers@xxxxxxxxxx>
Split get_key_and_iv() into two distinct parts: (1) deriving the key and
(2) generating the IV. Also, check for the presence of needed options
just before they are used rather than doing it all up-front.
These changes should make this code much easier to understand.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
src/fscrypt-crypt-util.c | 115 ++++++++++++++++++++++-----------------
1 file changed, 64 insertions(+), 51 deletions(-)
diff --git a/src/fscrypt-crypt-util.c b/src/fscrypt-crypt-util.c
index 022ff7bd..0ecf9272 100644
--- a/src/fscrypt-crypt-util.c
+++ b/src/fscrypt-crypt-util.c
@@ -1828,16 +1828,9 @@ static u32 hash_inode_number(const struct key_and_iv_params *params)
return (u32)siphash_1u64(hash_key.words, params->inode_number);
}
-/*
- * Get the key and starting IV with which the encryption will actually be done.
- * If a KDF was specified, a subkey is derived from the master key and the mode
- * number or file nonce. Otherwise, the master key is used directly.
- */
-static void get_key_and_iv(const struct key_and_iv_params *params,
- u8 *real_key, size_t real_key_size,
- union fscrypt_iv *iv)
+static void derive_real_key(const struct key_and_iv_params *params,
+ u8 *real_key, size_t real_key_size)
{
- int iv_methods = 0;
struct aes_key aes_key;
u8 info[8 + 1 + 1 + UUID_SIZE] = "fscrypt";
size_t infolen = 8;
@@ -1845,41 +1838,6 @@ static void get_key_and_iv(const struct key_and_iv_params *params,
ASSERT(real_key_size <= params->master_key_size);
- memset(iv, 0, sizeof(*iv));
-
- /* Overridden later for iv_ino_lblk_{64,32} */
- iv->block_number = cpu_to_le64(params->block_number);
-
- iv_methods += params->direct_key;
- iv_methods += params->iv_ino_lblk_64;
- iv_methods += params->iv_ino_lblk_32;
- if (iv_methods > 1)
- die("Conflicting IV methods specified");
- if (iv_methods != 0 && params->kdf == KDF_AES_128_ECB)
- die("--kdf=AES-128-ECB is incompatible with IV method options");
-
- if (params->direct_key) {
- if (!params->file_nonce_specified)
- die("--direct-key requires file nonce");
- if (params->kdf != KDF_NONE && params->mode_num == 0)
- die("--direct-key with KDF requires --mode-num");
- } else if (params->iv_ino_lblk_64 || params->iv_ino_lblk_32) {
- const char *opt = params->iv_ino_lblk_64 ? "--iv-ino-lblk-64" :
- "--iv-ino-lblk-32";
- if (params->kdf != KDF_HKDF_SHA512)
- die("%s requires --kdf=HKDF-SHA512", opt);
- if (!params->fs_uuid_specified)
- die("%s requires --fs-uuid", opt);
- if (params->inode_number == 0)
- die("%s requires --inode-number", opt);
- if (params->mode_num == 0)
- die("%s requires --mode-num", opt);
- if (params->block_number > UINT32_MAX)
- die("%s can't use --block-number > UINT32_MAX", opt);
- if (params->inode_number > UINT32_MAX)
- die("%s can't use --inode-number > UINT32_MAX", opt);
- }
-
switch (params->kdf) {
case KDF_NONE:
memcpy(real_key, params->master_key, real_key_size);
@@ -1896,24 +1854,28 @@ static void get_key_and_iv(const struct key_and_iv_params *params,
break;
case KDF_HKDF_SHA512:
if (params->direct_key) {
+ if (params->mode_num == 0)
+ die("--direct-key requires --mode-num");
info[infolen++] = HKDF_CONTEXT_DIRECT_KEY;
info[infolen++] = params->mode_num;
} else if (params->iv_ino_lblk_64) {
+ if (params->mode_num == 0)
+ die("--iv-ino-lblk-64 requires --mode-num");
+ if (!params->fs_uuid_specified)
+ die("--iv-ino-lblk-64 requires --fs-uuid");
info[infolen++] = HKDF_CONTEXT_IV_INO_LBLK_64_KEY;
info[infolen++] = params->mode_num;
memcpy(&info[infolen], params->fs_uuid, UUID_SIZE);
infolen += UUID_SIZE;
- iv->block_number32 = cpu_to_le32(params->block_number);
- iv->inode_number = cpu_to_le32(params->inode_number);
} else if (params->iv_ino_lblk_32) {
+ if (params->mode_num == 0)
+ die("--iv-ino-lblk-32 requires --mode-num");
+ if (!params->fs_uuid_specified)
+ die("--iv-ino-lblk-32 requires --fs-uuid");
info[infolen++] = HKDF_CONTEXT_IV_INO_LBLK_32_KEY;
info[infolen++] = params->mode_num;
memcpy(&info[infolen], params->fs_uuid, UUID_SIZE);
infolen += UUID_SIZE;
- iv->block_number32 =
- cpu_to_le32(hash_inode_number(params) +
- params->block_number);
- iv->inode_number = 0;
} else if (params->file_nonce_specified) {
info[infolen++] = HKDF_CONTEXT_PER_FILE_ENC_KEY;
memcpy(&info[infolen], params->file_nonce,
@@ -1928,9 +1890,60 @@ static void get_key_and_iv(const struct key_and_iv_params *params,
default:
ASSERT(0);
}
+}
- if (params->direct_key)
+static void generate_iv(const struct key_and_iv_params *params,
+ union fscrypt_iv *iv)
+{
+ memset(iv, 0, sizeof(*iv));
+ if (params->direct_key) {
+ if (!params->file_nonce_specified)
+ die("--direct-key requires file nonce");
+ iv->block_number = cpu_to_le64(params->block_number);
memcpy(iv->nonce, params->file_nonce, FILE_NONCE_SIZE);
+ } else if (params->iv_ino_lblk_64) {
+ if (params->block_number > UINT32_MAX)
+ die("iv-ino-lblk-64 can't use --block-number > UINT32_MAX");
+ if (params->inode_number == 0)
+ die("iv-ino-lblk-64 requires --inode-number");
+ if (params->inode_number > UINT32_MAX)
+ die("iv-ino-lblk-64 can't use --inode-number > UINT32_MAX");
+ iv->block_number32 = cpu_to_le32(params->block_number);
+ iv->inode_number = cpu_to_le32(params->inode_number);
+ } else if (params->iv_ino_lblk_32) {
+ if (params->block_number > UINT32_MAX)
+ die("iv-ino-lblk-32 can't use --block-number > UINT32_MAX");
+ if (params->inode_number == 0)
+ die("iv-ino-lblk-32 requires --inode-number");
+ iv->block_number32 = cpu_to_le32(hash_inode_number(params) +
+ params->block_number);
+ } else {
+ iv->block_number = cpu_to_le64(params->block_number);
+ }
+}
+
+/*
+ * Get the key and starting IV with which the encryption will actually be done.
+ * If a KDF was specified, then a subkey is derived from the master key.
+ * Otherwise, the master key is used directly.
+ */
+static void get_key_and_iv(const struct key_and_iv_params *params,
+ u8 *real_key, size_t real_key_size,
+ union fscrypt_iv *iv)
+{
+ int iv_methods = 0;
+
+ iv_methods += params->direct_key;
+ iv_methods += params->iv_ino_lblk_64;
+ iv_methods += params->iv_ino_lblk_32;
+ if (iv_methods > 1)
+ die("Conflicting IV methods specified");
+ if (iv_methods != 0 && params->kdf == KDF_AES_128_ECB)
+ die("--kdf=AES-128-ECB is incompatible with IV method options");
+
+ derive_real_key(params, real_key, real_key_size);
+
+ generate_iv(params, iv);
}
enum {
--
2.35.1
|